A typical toilet includes a tank filled with water and having a flush valve at its bottom. When a control handle is manually operated, water in the tank passes into a toilet bowl that may contain waste, to flush the waste through an upper trap and through a passage leading to a drain pipe. The water-filled upper trap prevents sewer gas from passing into the washroom. A water saver toilet typically reduces the amount of water passed into the bowl in each flushing, and uses a smaller toilet bowl to enable the contents of the bowl to be flushed out using less water. This usually results in a smaller “water spot,” which is the top of the pool of water in the bowl. Many people are uncomfortable with a small water spot in a shallow pool of water in the bowl, because waste may stack up above the water spot. A water saver toilet that provided a larger water spot and deeper pool of water in the bowl, and which enhanced a flushing, would be of value.
Flushing water can be saved by allowing the user to choose a partial flush when only liquid waste lies in the toilet bowl, and to choose a full flush when solid waste lie in the bowl. It would be desirable if such dual flush toilet used only a single flush valve to minimize the possibility of a leaking flush valve. Also, any less-than-vigorous flush should occur only during the partial flush when only liquid waste is being flushed, while a vigorous flush with rapidly moving flush water should occur during a full flush when solid waste is to be removed from the bowl.